The Stovebolt Site Forums The Shop Area The Electrical Bay Bad Dead Short

49 Chevy panel truck 6 volt system, I have a bad dead electrical short somewhere. History; completely replaced electrical wire harness, new battery, new fuses, starter and generator appear to be ok. Electrical system worked ok, engine although was always slow to crank over.

Vehicle went out for a paint job, and came back and would not start nor would the battery stay charged. While out being painted they left the key in the on position on more than one occasion, which could have burnt the points, but the points appear ok. I determined there was a dead short when I pulled the ground wire from the battery, recharged it and went to put the ground (negative) cable to the battery back on there was a real big spark indicating that there is a large drain(short) somewhere in the system.

Pulled the generator, regulator, and all five fuses and still there is a short. Took off the # 1 wire from the starter terminal to the amp meter and the short was then gone. I checked the harness behind the dash and there did not appear to be any disconnected or crossed wires, nothing touching the wires to the amp meter, and with the fuses to all the circuits out that would eliminate any shorted wires I think? Could the amp meter be shorted, or is the wire to the amp meter somehow shorted out. While out being painted they tried to start it once and it ran, but later (after they painted it) they attempted to start it, with no success. They attempted to charge it, but it would stay charged. Please, any ideas what is wrong, and how to fix it? Thanks for the help


God bless,


Dave

This is going to be a process of elimination and it sounds like you're on the right track. There may be a circuit or two that doesn't go through the fuse panel. Check your new wiring diagram to confirm this or, worse case, trace the wiring of BOTH sides of the ammeter. The horn, cigar lighter, and others may be wired direct and not go through the fuse panel.

It is possible that one of the ammeter terminals is grounded but not very likely unless they removed the guage cluster for painting. With a direct short like this there also may be burned or discolored wires that may help point you to the short.

Good hunting! Keep us posted.

Leave the wire off that goes from the starter cable to the ammeter, try to connect the battery cable, and see if the short goes away. It's possible there's a short in the starter. If isolating everything but the starter stops the short, it's somewhere downstream- - - -the ammeter or beyond.
Jerry

Thanks for the insight, but when I took the amp meter wire off and left the starter cable on the post of the starter the short went away. Thus this seems to eliminate the starter but the starter never did seem to turn the engine fast? Please keep the ideas coming.

Dave

OK, now take the cover off the voltage regulator, ands see if the point set right behind the BAT terminal is stuck together. That set of points is the "cutout relay" and should spring open anytime the engine stops. The other two sets of points are spring-closed.
Jerry

He mentioned that he "...pulled the generator, regulator...", I'm assuming the reg wires are hanging in the breeze already and that the short is hiding somewhere else. Is that right Panelit?

Hello:

Waldo, you are correct, the generator, regulator and all fuses are out, with no wires touching. It's when I removed the amp metere wire, wire # 1 is when the short stopped. The positive or starter wire was left in place on the starter and there was no short in this configuration. Ok what next, perhaps there is a wire directly to the amp meter, I will check and see. Thanks.

Regards,

Dave

Dave, if you have a test light you can do this a lot safer, when you're ready to see if the short is still there, put the test light between the neg battery post, and the ground strap. If it lights, you still have a short.

I don't remember if the brake light is fused in your truck, but if is is and the fuse is out, that eliminates the brake light switch keeping the brake light on. If the brake light is not fused, make sure your brake light switch is fully off when the pedal is fully retracted. Brake light switches sometimes will stick, or the pedal will hang a little low, which will keep the light on. If the switch is off, remove one wire from the switch to make sure it is out of the circuit.

Harvester

Not related to your short but, you mentioned your starter never turned the engine very fast. Be sure you are using big fat 6V battery cables and ground straps.

New discovery, when the negative cable is attached the amp meter pulses back and forth between negative and positive. What would this indicate? Thanks


Dave

bad regulator

Bill

Bill:

As stated, the generator and regulator were removed, they are currently in the shop for evaluation. Thus it is not the regulator. Thanks anyways. What else could it be?

Dave

Sheesh! This is going from bad to worse. Now, that sounds like a circuit breaker cycling. You're gonna hafta check your wiring diagram and probably get upside down under the dash and start eliminating things that are tied to the ammeter.

the ammeter should have a wire directly to the batt terminal on the starter and another to the key switch, and maybe one to the light switch, which does have bimetal 'circuit breakers' for the headlight circuit - is this 'pulsing' happening with the key OFF?

if the problem started after the body shop was goofing with it, it wouldn't be a suprise if they broke a wire or left something dangling, you need to recheck every wire in every circuit .... and don't hook up the battery again until everything is back in place, use an ohm meter on suspect wires, not a smoke test

Bill

Thank you again. On the amp meter there are four wires; the #1 wire on the + side of the meter which is the amp meter and coil feed wire, next is the # 14 wire on the + side of the meter which is the horn wire that goes to the fuse box on the fire wall and connects to wire # 26 which is the horn, next is a wire # 20 on the - side of the meter that goes to the BAT terminal of the regulator (remember the regulator is presently removed), next is a red wire, the feed to the turn signals, that connects to the amp meter. I pulled the fuse on this red wire and the problem remained. That’s the hook up as it presently stands. As mentioned before all fuses are out as is the generator.

Separately, I have a VOM meter, how do I use it on the OHMS setting to find a short and what level of ohms do I set it at? Thanks for your help and patience.


Regards,

Dave

do you have the wiring schematic? from the one here I see:
one wire from the (+) terminal to the starter switch
one wire from (+) to the fuse box [then to the horn]
one wire from the (-) terminal that splits [junction someplace, maybe directly on the ammeter] to: the lite sw, the regulator, the ign sw

that coil wire should come from the ign sw, a different terminal than the wire from the ammeter hooks to, if the coil wire hooks directly to the ammeter then the coil would be hot all the time

the wire for the turn signals is an add-on

you might have something on a wrong terminal somewhere [suspect coil to start], so you need to use the factory wiring diagram and trace the wires by their colors first, forget those numbers added by the harness maker, track the actual wire route and any intervening connections .... if all the existing wires go the correct places by the diagram, then the short checking starts

for short circuit testing one lead of the ohmeter to ground, the other to places being checked, any range will find a short, the lowest is usually used ... hope that's not all too confusing!

Bill

There's gotta be some junctions somewhere that feed the light switch and the ignition switch, both of which will have a link to the neg side of the ammeter and are hot all the time.

Caution: if you're going to use a VOM on a resistance scale, disconnect the pos. side of the battery. You don't want any voltage present when reading resistance - best case is faulty readings, worse case is a quick funeral for your meter.

waldo - yes, I should have mentioned battery disconnect, although knowing there's a serious shorting situation I assumed it wouldn't be connected .... OTOH, I would advise not having the battery hooked up under any condition while the reg/gen were out of the circuit, the main problem may just be that a loose wire is touching ground!!

also, looking back to the "bodyshop left the key in the on position on more than one occasion", the thought occurs that the problem could be a fried coil, which may be hooked to the wrong place anyway

Bill

Why is there a horn wire connected to the amp meter and then to a fuse box? That doesn't make any sense.

other way on the schematic nix, the ammeter feeds the fuse panel, which then feeds the horn, Dave is relating the harness makers numbering instructions, which may be confusing

Bill

I guess this must be a non standard harness. I think the standard setup has two fuses, one for tail lights and one for stop lights.

Waldo, Squeeze and all:

Thank you for all the tremendous insight you have given me. First, the wire harness is a standard wire harness made by Vintage Wire Harness of Maine. This company makes cloth covered wire harnesses to manufactures specs for most all make, model, and year of vehicles, with all the right color, correct type connectors, and related. I say this because the product is great and the company owner, Joe Hall, is probably one of the nicest and most helpful people that you ever want to talk to. If you’re in the market for a wire harness give this guy a call or email him at http://www.vintagewiringofmaine.com, I am not advertising for him rather bragging on the product, the service, and the man; all of which has been excellent.

Perhaps we are a bit far a field of matter, the wire harness has been in the truck for a year now and worked fine, until it went to the body shop. All hook ups are per standard and worked fine, until now. Something change in the last two week and the only thing that occurred is that it went to the body shop.

The wire coming off the negative of the amp meter is a singe #10 gage wire that goes to the BAT terminal on the regulator and also splits, in the harness, and feeds the head light switch and also goes to the starter switch, per standard. Squeeze, I think you are on to something as to the light switch, it has a bimetallic circuit breaker that could pulse if there was a ground.

Last night the Lord brought something to mind as I was praying on this, the truck while in the body shop
had a weld repair done to it on the drives side, just above the rear opening of the door. This is the same area where the wire goes to the dome light, and it is possible that the welder might have melted the wire while working in this area. I am going to check this out today and will get back to you on the outcome. The dome light is always hot so one can turn the light on while the truck is off.

Finally, A very great thanks to all, you have rallied around and have been a great source of help and encouragement. This forum works well and there are so many on it with great insight and experience. You have all been a great blessing. I will be back some as to the outcome of my findings.


God bless,


Dave

To all:

Again thank you, PTL, the problem is resolved, the wire to the dome light is shorted out, probably burnt when the welder was working. I will pull the damaged wire and replace same. Be well.

God bless,


Dave

Aha! This case is sol-ved (spoken with a heavy Clouseau accent).

Good sleuthing, no fair asking God for troubleshooting help though, how can we compete with Him?